A standing-room-only Christmas Eve crowd overflows St. Louis Cathedral. My early arriving mother-in-law managed to squeeze into a pew. For the rest of us, there is no room at the inn.

Keith Spera / The Times-PicayuneSophie, in princess pajamas, momentarily tears herself away from her new princess bicycle on Christmas morning.

In search of a second miracle — the first was rock-star parking directly behind the church — my wife and daughter make a pilgrimage up an aisle. A chivalrous woman cedes her seat to them.

Sam and I are on our own, stuck standing in steerage. From his perch in my arms, he strokes the heads and shoulders of nearby women.

“It’s him,” I reassure them.

The opening “O Come All Ye Faithful” inspires Sam to sing. His exuberant “aaahhhs!” and “acks!” continue after the music, resonating through the stilled sanctuary. Church, we conclude, is best left to the ladies.

Outside, the French Quarter huddles under a slate gray sky. Dress-shoe soles clack against Pere Antoine Alley flagstones. A skittish, feathered flock ignores “Church Quiet Zone” signs, chattering from perches in the few remaining trees along the cathedral’s rear fence.

At the intersection of Royal and St. Peter streets, Doreen’s Jazz New Orleans, a family ensemble led by clarinetist Doreen Ketchens, scoots through the standard “Bourbon Street Parade.”

“O Come All Ye Faithful” to “Bourbon Street Parade” — New Orleans in a nutshell.

Sam is in thrall. Ketchens’ band includes her tuba-playing husband, Lawrence, and the couple’s 9-year-old daughter, Dorian, on drums. They range from “Baby Please Come Home For Christmas” to “Silent Night.”

A scraggly gentleman sporting a prophet’s beard and dollars on his jacket calls out, “Merry Christmas, young man! Merry Christmas, young boy! Be safe tonight.”

A fuzzy brown dog on a leash pulls a skateboarder. A guy struts down St. Peter in sunglasses, an orange wig, black skirt, panty hose and a spangled gold bra. A Hare Krishna troupe parades by in a cacophony of shakers, cymbals and chants.

“It never stops,” Green notes.

At 6 p.m., Ketchens and company call it a night. Young Dorian abandons her drums for a pogo stick. Two dudes with indeterminate European accents — Swiss? German? Swedish? — sip Coronas on the curb and ask if she’s been good this year.

Back at St. Louis Cathedral, the priests have outlasted the jazz musicians. Sam and I settle onto a bench fronting the Cabildo. Behind us, a cruise ship glides along the Mississippi, towering over Jackson Square, its blazing white lights matching the square’s holiday décor.

A jester atop a plastic milk crate hustles tips for photos. As my wife, daughter and mother-in-law exit the cathedral, the jester intercepts them. He hones in on Sophie, correctly addressing her as “princess.” She tips him a Skittle. He eats it and solicits another. She refuses.

Even on Christmas Eve, the spirit of giving has its limits.

After church, we commune with a gaggle of uncles, aunts and cousins. Sophie is reluctant to leave, until the Santa tracker on the 10 o’clock news indicates the Big Guy is near. His impending arrival sparks a sense of urgency. She is concerned that our house lacks a chimney. How will Santa enter?

We will leave a door unlocked.

What if the dog barks at the reindeer?

He will realize they are authorized visitors.

Sophie sets out milk and homemade chocolate chip cookies for Santa, and eight carrots for reindeer. Poor Rudolph, with his nose so bright, is on his own.

The children nestled all snug in their beds, Santa’s helpers get to work. In the perennial favorite “A Christmas Story,” Ralphie covets a Red Ryder BB gun. In recent weeks, Sophie has fixated on a “princess bicycle.”

Thankfully Santa delivers. If not, her desperate father might have found himself scouring the Wal-Mart on Jefferson Highway, snatching the sole remaining princess bicycle from the display rack. Drew Brees is no prouder of his single-season passing record than I am of securing this bike.

Keith Spera / The Times-PicayunePresents? What presents? Sam is just fine swimming in a sea of wrapping paper.

It is a thing of beauty: Pink and silver handlebar streamers. A bell. Renderings of all major princesses. Flower-petal pedals. At home, I savor the scent of the white rubber wheels. They smell like...victory.

Exhaustion takes a toll. Some miscue of mine triggers an un-seasonably strong rebuke from my wife.

“I don’t think elves talk like that,” I note.

“They do when Santa acts like that,” she counters.

The next morning, Sophie and Sam bestow the greatest possible Christmas gift: They sleep until 9 a.m.

Sophie peeks into the den before bounding into our bedroom. “Santa came! Santa came! I was on the good list! I didn’t get changed to the naughty list!”

She is visibly relieved. She bursts into her baby brother’s darkened room. “Sam, wake up! Santa came to our house!”

Momentarily stunned, Sam does not share her enthusiasm. A fresh diaper would suffice as a gift for him.

Downstairs, Sophie scans wrapped presents, calculating what each might contain. Mommies prefer gifts in small boxes; for 4-year-olds, the bigger, the better.

Sophie pounces on the largest box under the tree; alas, it belongs to her brother. She tears through her pile as Sam swims in a sea of wrapping paper. Ralphie-like, she masks disappointment and pronounces herself pleased, even though her Red Ryder BB gun is nowhere to be found.

Hey, honey — what’s that on the porch?

She discovers the stumps of two carrots, gnawed, no doubt, by ravenous reindeer.

And … a princess bicycle.

Her shriek of elation is audible all the way to the North Pole: “This is what I wanted!!!”

She will soon learn that bumps and bruises are part of learning to ride. Eventually she will outgrow the princess bicycle; in time, its luster will fade. But the memory of its unveiling never will.

Thanks, Santa.

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Keith Spera can be reached at kspera@timespicayune.com or 504.826.3470. Read more from “The Paternity Test” at nola.com/family. Follow him at twitter.com/KeithSperaTP.